I posted about Captchas–those squiggly barely-decipherable words used to filter robots from accessing protected websites–two years ago.  Their story is fascinating, not well-known, and worth mentioning again.  Even the name is cool:  Captcha is an acronym for “completely automated public Turing test to tell computers and humans apart.”  As the NY Times reported Monday Captchas serve a purpose in addition to separating humans from machines:  they are bits of text from old books that require correction after the books have been scanned.  Invented by researchers at Carnegie Mellon University they are used by the Google Book Project, the New York Times, and others transforming old and archival materials into accurate digital copy.  It’s brilliantly simple:  allow thousands of computer users to interpret unclear text snippets, collate the results, deduce the correct meaning.  The Carnegie Mellon researchers estimate that “humans around the world decode at least 200 million Captchas per day, at 10 seconds per Captcha. This works out to about 500,000 hours per day . . .”  This explains why some Captchas are impossible to decode. They are flyspecked text from musty centuries-old books.

3 Replies to “Captcha”

  1. Natalie

    This is insane! I would always get so frustrated with those letterings; more recently it was happening when I would try to send e-mails. I think it is the coolest thing that they are previously coded books, I it is incredible to see that it is a way to distinguish between human and computer.

  2. Diana Lau

    I also had no idea that Captchas served this purpose and from now on, I'll actually feel better every time I am required to decode one. It really is a pain because sometimes it takes a few tries. I always wondered why they just couldn't make the words more legible to read. This just goes to show that there is always more to something than the eye can see.

  3. Anand Brahmbhatt

    This is so crazy, and brilliant. I persistently deactivate my facebook account when I have exams, and when I deactivate it – I have to actually fill in this information. I didn't know I was doing this for a greater good. This is really astonishing to me, and I just told my friend about it who said that sometimes she just can't figure it out. I went onto read her the last few lines from the blog article. This is crazy, because it just shows you how much a few seconds a day by millions of people can do.

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